Impact of herbage proportion, animal breed, lactation stage and season on the fatty acid and protein composition of milk

Abstract Impact of herbage proportion, breed, average days in lactation (ADiL), and season on bulk milk composition of 12 dairy farms were investigated over a year using a mixed effect model approach. A higher proportion of herbage led to higher contents of omega 3 (n-3) fatty acids (FAs), conjugated linoleic acids (CLA), vaccenic acid, and branched chain FAs (+0.08, +0.08, +0.19, +0.05 g 100 g-1 fat, respectively). Breed influenced n-3 FAs and CLA (+0.31, +0.17 g 100 g-1 fat, respectively), κ-casein, lipoprotein lipase, β-lactoglobulin, total whey protein, fatty acid synthase, and glycoprotein-2, resulting in +0.96, –0.019, –0.83, –1.12, +0.009, and +0.01 g 100 g-1 measured proteins, respectively, in Brown Swiss milk. ADiL influenced lactoferrin and crude protein; season affected all FAs and proteins examined. The identification of these quantitative relationships allow predictions that provide new insights for the production, processing and commercialisation of grassland-based dairy products.